1. Field of the Invention
The present invention relates to measuring and controlling electromagnetic interference caused by electronic devices.
2. Background of the Related Art
Electromagnetic interference (“EMI”) is a problem wherein an electronic circuit radiates unwanted electromagnetic radiation (“EMR”), i.e. electromagnetic noise, having the potential to interfere with the operation of other electronic circuits. Metal substructures within an electronic system often serve as efficient radiating or reflecting antennas for EMR. Examples of such metal substructures include, but are not limited to, processor heatsinks, printed circuit board (“PCB”) reference planes, and interconnecting brackets. Existing approaches to controlling EMR include adding a Faraday shield around the entire metal substructure, or reducing the size of apertures in a metal enclosure to improve shielding at higher frequencies. Spread-spectrum clocking is also an option, but is not compatible with many circuits that cannot tolerate the resulting clock skew. Reducing EMI is particularly challenging at higher processor clock frequencies because the correspondingly smaller EMR wavelengths are more difficult to contain by conventional shielding methods.